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Sensors (Basel, Switzerland) Oct 2019This review summarizes the latest developments in the field of skin chemical sensors, in particular wearable ones. Five major applications are covered in the present... (Review)
Review
This review summarizes the latest developments in the field of skin chemical sensors, in particular wearable ones. Five major applications are covered in the present work: (i) sweat analysis, (ii) skin hydration, (iii) skin wounds, (iv) perspiration of volatile organic compounds, and (v) general skin conditions. For each application, the detection of the most relevant analytes is described in terms of transduction principles and sensor performances. Special attention is paid to the biological fluid collection and storage and devices are also analyzed in terms of reusability and lifetime. This review highlights the existing gaps between current performances and those needed to promote effective commercialization of sensors; future developments are also proposed.
Topics: Humans; Sensation; Skin; Sweat; Volatile Organic Compounds; Wearable Electronic Devices
PubMed: 31658706
DOI: 10.3390/s19204376 -
Journal of Thermal Biology Oct 2020The purpose of this study was to determine local sweat rate (LSR) and sweat composition during heat acclimation (HA). For ten consecutive days of HA, eight participants...
The purpose of this study was to determine local sweat rate (LSR) and sweat composition during heat acclimation (HA). For ten consecutive days of HA, eight participants cycled in 33 °C and 65% relative humidity at an intensity such that a rectal temperature of 38.5 °C was reached within ~40 min, followed by a 60-min clamp of this rectal temperature (i.e., controlled hyperthermia). Four participants extended HA by a 28-day decay period and five consecutive days of heat re-acclimation (HRA) using controlled hyperthermia. Sweat from the upper arm and upper back was collected three times during each heat exposure session. LSR and sweat sodium, chloride, lactate, and potassium concentrations were determined. Relative to HA day 1, LSR was increased at the final day of HA (day 10) (arm: +58%, P < 0.001; back: +36%, P < 0.05). Concentrations of sodium, chloride, and lactate significantly (P < 0.05) decreased to ~60% at HA day 10 compared to day 1 on the arm and back. Potassium concentration did not significantly differ on HA day 10 compared to day 1 (arm: +11%, P > 0.05; back: +8%, P > 0.05). The induction patterns of the sudomotor adaptations were different. Whilst LSR increased from HA day 8 on the arm and from HA day 7 on the back, sodium and chloride conservation already occurred from HA day 3 on both skin sites. Lastly, the sweat lactate reduction occurred from HA day 6 on the arm and back. Initial evidence is provided that adaptations were partly conserved after decay (28 days) and that a 5-day HRA may be sufficient to restore HA adaptations. In conclusion, ten days of exercise-induced HA using controlled hyperthermia led to increases in LSR and concomitant reductions of sweat sodium, chloride, and lactate concentrations, whilst potassium concentrations remained relatively constant.
Topics: Acclimatization; Adult; Chlorides; Female; Hot Temperature; Humans; Lactic Acid; Male; Middle Aged; Potassium; Sodium; Sweat; Sweating
PubMed: 33077118
DOI: 10.1016/j.jtherbio.2020.102697 -
Medical Science Monitor : International... Jun 2024BACKGROUND This study explored the integration of conductive threads into a microfluidic compact disc (CD), developed using the xurographic method, for a potential sweat...
BACKGROUND This study explored the integration of conductive threads into a microfluidic compact disc (CD), developed using the xurographic method, for a potential sweat biosensing platform. MATERIAL AND METHODS The microfluidic CD platform, fabricated using the xurographic method with PVC films, included venting channels and conductive threads linked to copper electrodes. With distinct microfluidic sets for load and metering, flow control, and measurement, the CD's operation involved spinning for sequential liquid movement. Impedance analysis using HIOKI IM3590 was conducted for saline and artificial sweat solutions on 4 identical CDs, ensuring reliable conductivity and measurements over a 1 kHz to 200 kHz frequency range. RESULTS Significant differences in |Z| values were observed between saline and artificial sweat treatments. 27.5 μL of saline differed significantly from 27.5 μL of artificial sweat, 72.5 μL of saline from 72.5 μL of artificial sweat, and 192.5 μL of saline from 192.5 μL of sweat. Significant disparities in |Z| values were observed between dry fibers and Groups 2, 3, and 4 (varying saline amounts). No significant differences emerged between dry fibers and Groups 6, 7, and 8 (distinct artificial sweat amounts). These findings underscore variations in fiber characteristics between equivalent exposures, emphasizing the nuanced response of the microfluidic CD platform to different liquid compositions. CONCLUSIONS This study shows the potential of integrating conductive threads in a microfluidic CD platform for sweat sensing. Challenges in volume control and thread coating degradation must be addressed for transformative biosensing devices in personalized healthcare.
Topics: Sweat; Biosensing Techniques; Humans; Lab-On-A-Chip Devices; Microfluidics; Electric Conductivity; Electrodes; Electric Impedance
PubMed: 38863180
DOI: 10.12659/MSM.943321 -
Journal of Cystic Fibrosis : Official... May 2022CFTR is an anion channel that causes cystic fibrosis (CF) when its activity, equal to channel number x open probability x conductance (n·P·γ) is absent or nearly so.... (Review)
Review
CFTR is an anion channel that causes cystic fibrosis (CF) when its activity, equal to channel number x open probability x conductance (n·P·γ) is absent or nearly so. CFTR modulators increase CFTR activity, but estimates of in vivo efficacy vary. This review shows how values from the simple and widely used sweat chloride test can be calibrated to provide more accurate estimates of CFTR activity as a percent of the average for healthy control (HC) subjects (hereafter 'CFTR activity'). Sweating stimulated by β-adrenergic agonists (β-sweat) is rate-limited by CFTR, producing a near linear, ratio scale of CFTR activity with carriers = 50% and CF = 0% of HC values set = 100%, but the β-sweat assay is difficult to use. Here, sweat chloride is calibrated to CFTR activity by plotting mean sweat chloride values, taken from numerous studies and the CFTR2 database against mean β-sweat rates for CF, carriers and HC. The resulting inverse logarithmic relations indicate that sweat chloride values ≥60 mmol/L occur when CFTR activity is below 1.2% -10% of HC. These are lower than most previous estimates, which resulted from setting nasal potential difference (NPD) as linear rather than logarithmic measures of CFTR activity. Features of the sweat gland coil and duct are used to explain why readouts of CFTR activity are linear for β-sweat and logarithmic for sweat chloride. Sweat chloride values fall steeply for small increments of CFTR activity above zero-the most clinically relevant region. Thus, large health benefits can be achieved by restoring low levels of CFTR activity, especially if this is done before irreversible lung damage. Truncated Abstract: CFTR is an anion channel that causes cystic fibrosis (CF) when its activity, equal to channel number x open probability x conductance (n·P·γ) is absent or nearly so. CFTR modulators increase CFTR activity, but estimates of in vivo efficacy vary. This review shows how values from the sweat chloride test can be calibrated to provide accurate estimates of CFTR activity as a percent of the average for healthy control (HC) subjects. Sweating stimulated by β-adrenergic agonists is rate-limited by CFTR, producing a near linear, ratio scale of CFTR activity, but the assay is difficult to use. Here, sweat chloride is calibrated to CFTR activity by plotting it against mean β-sweat rates for different groups. The resulting logarithmic relations indicate that CF sweat chloride values occur when CFTR activity is below 1.2% -10% of HC, and that large health benefits can be achieved by restoring low levels of CFTR activity if this is done early.
Topics: Adrenergic beta-Agonists; Chlorides; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Humans; Mutation; Sweat; Sweat Glands
PubMed: 35184981
DOI: 10.1016/j.jcf.2022.02.001 -
Skin Research and Technology : Official... Mar 2022While sunbathing of performing outdoor sport activities, sunscreens are important for protection of uncovered skin against ultraviolet (UV) radiation. However,...
BACKGROUND
While sunbathing of performing outdoor sport activities, sunscreens are important for protection of uncovered skin against ultraviolet (UV) radiation. However, perspiration negatively affects the performance of a sunscreen film by weakening its substantivity and uniformity through the activation of two mechanisms, namely sunscreen wash-off and sunscreen redistribution.
MATERIAL AND METHODS
We used a perspiring skin simulator to investigate the effect of sunscreen formulation on its efficiency upon sweating. Specifically, we modified the sunscreen formulation by incorporating a hydrophobic film former and adding water-absorbing particles. Sunscreen performance before and after perspiration is assessed by in vitro sun protection factor measurements, direct detection of changes in the sunscreen distribution using UV reflectance imaging, and by coherent anti-Stokes Raman scattering (CARS) microscopy for microscopic characterization of the UV filter relocation.
RESULTS
The results show that incorporating a hydrophobic film former can decrease sunscreen wash-off due to sweating, while an excessive amount of film former might negatively affect the sunscreen distribution. The addition of water-absorbing particles, on the other hand, had either a negative or positive impact on the sunscreen substantivity, depending on the particle properties. While the addition of large water-absorbing particles appeared to increase sunscreen redistribution, smaller particles that could form a gel-like structure upon contact with water, appeared to change sunscreen wetting and sweat droplet spreading, thereby decreasing sunscreen wash-off and sunscreen redistribution.
CONCLUSIONS
We find that using a combination of hydrophobic film formers, which increase water resistance, and small water-absorbing particles, which change the wetting behavior, can make sunscreen formulations more sweat-resistant and less runny.
Topics: Humans; Skin; Sunscreening Agents; Sweat; Sweating; Ultraviolet Rays
PubMed: 34752663
DOI: 10.1111/srt.13115 -
Biosensors Nov 2022Wearable devices are being developed faster and applied more widely. Wearables have been used to monitor movement-related physiological indices, including heartbeat,...
Wearable devices are being developed faster and applied more widely. Wearables have been used to monitor movement-related physiological indices, including heartbeat, movement, and other exercise metrics, for health purposes. People are also paying more attention to mental health issues, such as stress management. Wearable devices can be used to monitor emotional status and provide preliminary diagnoses and guided training functions. The nervous system responds to stress, which directly affects eye movements and sweat secretion. Therefore, the changes in brain potential, eye potential, and cortisol content in sweat could be used to interpret emotional changes, fatigue levels, and physiological and psychological stress. To better assess users, stress-sensing devices can be integrated with applications to improve cognitive function, attention, sports performance, learning ability, and stress release. These application-related wearables can be used in medical diagnosis and treatment, such as for attention-deficit hyperactivity disorder (ADHD), traumatic stress syndrome, and insomnia, thus facilitating precision medicine. However, many factors contribute to data errors and incorrect assessments, including the various wearable devices, sensor types, data reception methods, data processing accuracy and algorithms, application reliability and validity, and actual user actions. Therefore, in the future, medical platforms for wearable devices and applications should be developed, and product implementations should be evaluated clinically to confirm product accuracy and perform reliable research.
Topics: Humans; Reproducibility of Results; Wearable Electronic Devices; Biosensing Techniques; Athletic Performance; Sweat; Monitoring, Physiologic
PubMed: 36551064
DOI: 10.3390/bios12121097 -
Allergology International : Official... Jan 2021Cholinergic urticaria (CholU) manifests small, itchy and/or painful wheals occurring upon perspiration and mechanically involving acetylcholine (Ach). Although a... (Review)
Review
Cholinergic urticaria (CholU) manifests small, itchy and/or painful wheals occurring upon perspiration and mechanically involving acetylcholine (Ach). Although a considerable number of studies have been conducted, the pathomechanisms underlying perspiration-associated release of histamine remain to be elucidated. We have proposed that CholU can be categorized into two major subtypes: Ach-indirectly induced, sweat allergic type and Ach-directly induced, depressed sweating type. In the former type, Ach evokes perspiration, and some sweat antigen(s) leaking from the sweat ducts to the dermis may stimulate mast cells to release histamine. In this scenario, the ducts might be damaged or obstructed for sweat leakage, and patients frequently exhibit positive autologous sweat skin test, representing "sweat allergy (hypersensitivity)". On the other hand, the latter Ach-mast cell directly interacting type, typically seen as "CholU with anhidrosis and/or hypohidrosis (CUAH)", eccrine sweat gland epithelial cells lack cholinergic receptor M3 expression. The expression of cholinergic receptors is completely absent in the anhidrotic areas and only slightly expressed in the hypohidrotic areas. In the hypohidrotic area, where pinpoint wheal occurs, it is hypothesized that released Ach cannot be completely trapped by cholinergic receptors of eccrine glands and overflows to the adjacent mast cells, leading to wheal formation. Thus, sweat allergy is not a requirement in this depressed sweating type. Although some additional complications, such as angioedema, anaphylaxis, and cold urticaria, have been documented, these two types represent the modes of action of Ach in this enigmatic urticaria.
Topics: Acetylcholine; Allergens; Biomarkers; Disease Susceptibility; Gene Expression Regulation; Histamine; Histamine Release; Humans; Immunoglobulin E; Mast Cells; Receptors, Cholinergic; Skin Tests; Sweat; Urticaria
PubMed: 32565175
DOI: 10.1016/j.alit.2020.05.006 -
ACS Applied Bio Materials Jan 2021The recent advent of biodegradable materials has offered huge opportunity to transform healthcare technologies by enabling sensors that degrade naturally after use. The... (Review)
Review
The recent advent of biodegradable materials has offered huge opportunity to transform healthcare technologies by enabling sensors that degrade naturally after use. The implantable electronic systems made from such materials eliminate the need for extraction or reoperation, minimize chronic inflammatory responses, and hence offer attractive propositions for future biomedical technology. The eco-friendly sensor systems developed from degradable materials could also help mitigate some of the major environmental issues by reducing the volume of electronic or medical waste produced and, in turn, the carbon footprint. With this background, herein we present a comprehensive overview of the structural and functional biodegradable materials that have been used for various biodegradable or bioresorbable electronic devices. The discussion focuses on the dissolution rates and degradation mechanisms of materials such as natural and synthetic polymers, organic or inorganic semiconductors, and hydrolyzable metals. The recent trend and examples of biodegradable or bioresorbable materials-based sensors for body monitoring, diagnostic, and medical therapeutic applications are also presented. Lastly, key technological challenges are discussed for clinical application of biodegradable sensors, particularly for implantable devices with wireless data and power transfer. Promising perspectives for the advancement of future generation of biodegradable sensor systems are also presented.
Topics: Biocompatible Materials; Biopolymers; Body Temperature; Breath Tests; Electrodes, Implanted; Humans; Monitoring, Physiologic; Pressure; Semiconductors; Sweat
PubMed: 33842859
DOI: 10.1021/acsabm.0c01139 -
Scientific Reports Nov 2020Cortisol is a biomarker for stress monitoring; however, the biomedical and clinical relevance is still controversial due to the complexity of cortisol secretion...
Cortisol is a biomarker for stress monitoring; however, the biomedical and clinical relevance is still controversial due to the complexity of cortisol secretion mechanisms and their circadian cycles as well as environmental factors that affect physiological cortisol level, which include individual mood and dietary intake. To further investigate this multifaceted relationship, a human pilot study examined cortisol concentration in sweat and saliva samples collected from 48 college-aged participants during aerobic exercise sessions along with mental distress and nutrition surveys. Enzyme-linked immunosorbent assays determined highly significant differences between apocrine-dominant sweat (AP), saliva before exercise (SBE), and saliva after exercise (SAE) cortisol concentration (AP-SBE: p = 0.0017, AP-SAE: p = 0.0102). A significantly greater AP cortisol concentration was detected in males compared to females (p = 0.0559), and significant SAE cortisol concentration differences were also recorded between recreational athletes and non-athletes (p = 0.044). However, Kessler 10 Psychological Distress Scale (K10) scores, an examination administered to deduce overall wellness, provided no significant differences between males and females or athletes and non-athletes in distress levels, which statistically signifies a direct relationship to cortisol was not present. For further analysis, dietary intake from all participants was considered to investigate whether a multiplexed association was prevalent between nutrition, mood, and cortisol release. Significant positive correlations between AP cortisol, SAE cortisol, K10 scores, and fat intake among female participants and athletes were discovered. The various machine learning algorithms utilized the extensive connections between dietary intake, overall well-being, sex factors, athletic activity, and cortisol concentrations in various biofluids to predict K10 scores. Indeed, the understanding of physiochemical stress response and the associations between studied factors can advance algorithm developments for cortisol biosensing systems to mitigate stress-based illnesses and improve an individual's quality of life.
Topics: Adult; Affect; Biomarkers; Body Fluids; Diet; Exercise; Female; Humans; Hydrocortisone; Machine Learning; Male; Nutritional Status; Saliva; Stress, Physiological; Stress, Psychological; Surveys and Questionnaires; Sweat; Young Adult
PubMed: 33149196
DOI: 10.1038/s41598-020-75871-3 -
Journal of the Royal Society, Interface Oct 2019The state-of-the-art in wearable flexible sensors (WFSs) for sweat analyte detection was investigated. Recent advances show the development of integrated, mechanically... (Review)
Review
The state-of-the-art in wearable flexible sensors (WFSs) for sweat analyte detection was investigated. Recent advances show the development of integrated, mechanically flexible and multiplexed sensor systems with on-site circuitry for signal processing and wireless data transmission. When compared with single-analyte sensors, such devices provide an opportunity to more accurately analyse analytes that are dependent on other parameters (such as sweat rate and pH) by improving calibration from real-time analysis, while maintaining a lightweight and wearable design. Important health conditions can be monitored and on-demand regulating drugs can be delivered using integrated wearable systems but require correlation verification between sweat and blood measurements using validation tests before any clinical application can be considered. Improvements are necessary for device sensitivity, accuracy and repeatability to provide more reliable and personalized continuous measurements. With rapid recent development, it can be concluded that non-invasive WFSs for sweat analysis have only skimmed the surface of their health monitoring potential and further significant advancement is sure to be made in the medical field.
Topics: Humans; Monitoring, Physiologic; Signal Processing, Computer-Assisted; Sweat; Wearable Electronic Devices
PubMed: 31594525
DOI: 10.1098/rsif.2019.0217